Lock cylinder assembly

ABSTRACT

A core of a conventional tumbler-type lock cylinder assembly includes an additional rib which receives only an additional groove in the free end of the bitted portion of the key to increase the number of usable lock combinations.

United States Patent [72] Inventor Theodore H. Johnstoue New Baltimore,Mich. [211 AppLNo. 791,112 [22] Filed Jan. 14, 1969 I45] Patented Aug.10, 1971 [7 3] Assignee General Motors Corporation Detroit, Mich.

[541 LOCK CYLINDER ASSEMBLY 1 Claim, 4 Drawing Figs.

[52] US. Cl 1. 70/364 R, 70/406, 70/453 [51] Int. Cl E051) 15/08, 1305b19/06 [50] Field of Search 70/364, 364 A, 375, 382, 405, 406, 419, 420,421, 453, 454, 403, 404, 407

[56] References Cited UNITED STATES PATENTS 246,438 8/1881 Woolaston eta1. 70/363 Primary Examiner-Jan A. Calvert Assistant ExaminerRobert L.Wolfe Attorneys-E. W. Christen and Herbert Furman Bod ge Spain TaylorFOREIGN PATENTS Switzerland France tions.

LOCK CYLINDER ASSEMBLY This invention relates to lock cylinderassemblies and more particularly to a lock cylinder assembly having anincreased number oflock combinations. I i

The number of lock combinations which normally can be obtained from atumbler-type lock is affected by the number of tumblers included in thelock. Generally the number of theoretical combinations is much greaterthan the number of usable combinations.

In order to increase the number ofcombinations without increasing thenumber of tumblers, it is conventional to provide a ribbed gate in thecore and grooves in the key which must mate with the ribs of the gatebefore the key can be inserted in the core to properly locate thetumblers in their unlocked position. Due to space and manufacturinglimitations, the number of such ribs and grooves is limited so that theincrease in number oflock combinations is likewise limited.

The lock cylinder assembly of this invention increases the number oflock combinations by having an additional rib within the core remotefrom the ribbed gate and receiving an additional groove in the leadingend of the bitted portion of the key when the key is fully insertedwithin the core. The core rib is unaligned with any other core rib andlikewise the key groove is unaligned with any other key groove so thatonly a properly grooved key can be fully inserted in order to locate thetumblers in their unlocked position. By varying the location of theinterfitting additional rib and groove, in combination with varying thelocation of the ribs on the gate and grooves on the key, an increase inthe number of possible lock combinations can be obtained within thenormal manufacturing and space limitations By locating the additionalrib remote from the gate and by locating the groove in the leading endof the bitted portion of the key, it is impossible for an imroperlycoded key to move all of the tumblers to unlocked position by partialinsertion of the key.

The primary object of this invention is to provide a lock cylinderassembly having an increased number of lock combinations. Another objectof this invention is to provide a lock cylinder assembly having anadditional rib within the core remote from the gate and receiving anadditional groove in the leading end of the bitted portion of the key,both unaligned with any other ribs and grooves, to thereby provide anincrease in the number of usable lock combinations.

These and other objects of the invention will be readily apparent fromthe following specification and drawings wherein:

FIG. I is a partially cutaway view of a lock cylinder assembly accordingto this invention;

FIG. 2 is a sectional view taken generally along the plane indicated byline 2-2 of FIG. 1;

FIG. 3 is a view taken generally along the plane indicated by line 3-3of FIG. 1; and

FIG. 4 is a view similar to FIG. I showing the assembly with the keywithdrawn.

Referring now to FIG. 1 of the drawings, the lock cylinder assembly ofthis invention includes a conventional side bar lock cylinder 10 havinga core 12 mounting a plurality of shiftable tumblers 14, best shown inFIG. 2, each of which includes a notch I6. When the notches 16 arealigned upon insertion ofa properly coded key, a side bar 18 movesinwardly of the core to permit the core to rotate within the outer case20 of the assembly. This is conventional in currently used side bar lockcylinder assemblies.

The key 22 includes a bitted portion 24 which, when inserted within thecore, locates the tumblers 14 in their unlocked position to align thenotches I6. In order to increase the number of lock combinations, thecore 12 includes a conventional gate 26 provided with one or more ribs28, and the key 22 includes respective grooves 30 on the bitted portion24 which slide relative to the ribs when the key is inserted. By varyingthe location of the ribs 28 and grooves 30, the number ofloekcombinations is increased.

Due to space and manufacturing limitations, there are only a limitednumber of possible locations of the ribs 28 and grooves 30 so that thenumber of lock combinations can only be increased by a limited amount.

In accordance with this invention, the core 12 includes an additionalrib 32 on a wall of a recess 34 thereof which receives the leading endof the bitted portion of the key when the key is inserted. An additionalgroove 36 on a wall of the key receives the additional rib 32. Byvarying the location of the rib 32 and groove 36, the number of possiblelock combinations is increased.

With reference to FIGS. 2 and 3, it can be seen that the rib 32 isunaligned with any other rib in the core 12 and likewise the groove 36is unaligned with any other groove in the particular wall of the key.

Thus this invention provides a lock cylinder assembly having anincreased number of lock combinations without increasing the number oftumblers.

'Iclaim:

l. A lock cylinder assembly including a core mounting a plurality ofkeylocatable tumblers and defining a slot, a key having a flattenedbitted portion receivable within the slot wherein the lateral sides ofthe bitted portion include grooves Y for receiving ribs fixed withrespect to the core and extending axially thereof adjacent the openingof the slot, an additional lateral rib fixed with respect to the coreadjacent the end of the slot remote from the opening thereof, theadditional lateral rib extending axially of the core for a limiteddistance with respect to the bitted portion when inserted within theslot, and an additional lateral groove at the free end of the bittedportion extending for such limited distance and receiving the additionallateral rib when the bitted portion is inserted within the slot, theadditional lateral rib and the additional lateral groove being unalignedwith any rib or groove adjacent the opening of the slot.

1. A lock cylinder assembly including a core mounting a plurality ofkey-locatable tumblers and defining a slot, a key having a flattenedbitted portion receivable within the slot wherein the lateral sides ofthe bitted portion include grooves for receiving ribs fixed with respectto the core and extending axially thereof adjacent the opening of theslot, an additional lateral rib fixed with respect to the core adjacentthe end of the slot remote from the opening thereof, the additionallateral rib extending axially of the core for a limited distance withrespect to the bitted portion when inserted within the slot, and anadditional lateral groove at the free end of the bitted portionextending for such limited distance and receiving the additional lateralrib when the bitted portion is inserted within the slot, the additionallateral rib and the additional lateral groove being unalined with anyrib or groove adjacent the opening of the slot.